(for an upcoming change where I wanted to easily distinguish these
two)
Change-Id: Icb6a0144275cc9bf8978a7cb96b601d516d8da46
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Mostly so the Linux one can use Linux-specific stuff in package
syscall and not use os/exec for uname for portability.
But also it helps deps a tiny bit on iOS.
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>